One of my most-favorite lines ever in a UGA Extension publication is about summer squashes. The line is in a table that lists recommended varieties for each type of crop. It says, for which varieties of summer squashes (including zucchini) to plant in the garden, “all are good and easy to grow.”
This line still makes me laugh. In a way, it matches my experience. In early summer the plants look great and produce plenty of flowers and small squashes. Unfortunately, it could also read “all are finicky and frustrating to grow”, since many summer-squash plants seem to drop into wilted piles of yellowing leaves in mid-summer, long before we have eaten too much squash. When I first started gardening in Georgia, I was lucky to get five or six good-sized squashes from a plant before it keeled over.
Southern Vs. Northern Experiences with Summer Squash
I am not the only Southern gardener to be troubled by a too-small squash harvest or plants that die too soon. However, Northern gardeners do not seem to have this problem. The complaint I hear from Northern gardeners is quite the opposite – they have mountainous harvests of zucchini and yellow squashes that keep coming all summer long.
Really, the complaint is one that doubles as a brag – their squashes are so very productive that, when the harvests begin, it is risky to leave your car windows open. The risk is that gardeners who have a superabundance of squash are likely to drop a large bag of squashes into the car as “a gift”.
Legend has it that over-squashed gardeners also will fill a bag with squashes, hang the bag on the doorknob of an unsuspecting neighbor’s home, ring the doorbell, and run. By the end of August, people are totally tired of squashes, especially zucchini.
I have never had so much summer squash and zucchini that I was not happy to find another one in the garden. Happily, as I have gained experience and understanding of what is going on in the garden, my plants survive longer and the harvests are larger. I have found that it is possible to have plenty of summer squash in the Southern garden, with a little planning.
Problems with Summer Squash in the Southern Garden
Squash Vine Borers
These are the cause of much anguish in the squash patch. The borers are larvae (caterpillars) of a day-flying moth that lays its eggs on stems of our squash plants. When the eggs hatch, the babies bore into stem, where they eat the soft part of the inside of the stem. The borers seem to not eat the toughest fibers, because one sign that borers have caused your squash plants to wilt is that the stem looks frayed. You may also see some frass (caterpillar poo), a golden-orange-brown, granular-looking mush, around or in the damaged section of stem.
What to do? If the plant is already a wilted mass of yellowing leaves, it may be too late to save the plant. If, though, you look at the lower part of a squash stem, see little holes in the stem and maybe a little frass nearby, but the plant looks otherwise healthy, it is not too late!
Locate the sharpest blade on your pocket knife and use it to make a long slit in one side of the squash stem. The slit should run lengthwise on the stem; it should start below where the damage seems to be and extend above the damaged area. Use the tip of the knife blade to pry the slit open, so you can look inside and find the squash vine borers. Use the knife tip to remove (or kill, depending on your philosophical stance on garden pests) the borers from the stem. You might find just one, but you might find a half dozen or more.
Saturate the inside of the stem with a product that contains Bt for caterpillars (Thuricide is the brand I have been using – bought a few years ago and still works), and spray up the length of the stem on the outside, too. If any borers are still alive inside the stem, the Bt for caterpillars (organic approved) should reverse that status fairly soon. If your Bt is powder form instead of liquid, do your best to fill the stem with the powder, and then liberally apply it along the outside of the stem.
Any Bt applied on the outside of the stem will wash away in the next rain or watering-event, so you might want to re-apply it a few times.
Mound up garden soil over the damaged section of stem. If you are feeling very industrious, you can try wrapping the damaged section with aluminum foil, but I find that just piling up some good soil over the damaged stem protects it from invasion by other pests. Also, squashes sometimes will send out new roots along buried sections of stem.
Consider the health-status of your plant. Summer squash in the Southern garden should be lush, with huge, dark green leaves. In my garden, the largest, fastest-growing squash plants survive squash vine borer damage much better than less-lush plants. If your plants are on the puny-side, side-dress with some organic fertilizer or a shovel-full of compost or composted manure.
Squash bugs look a lot like stink bugs as adults. As youngsters, they are called nymphs, and they move around in groups. The nymphs do not look at all like the adults, but if you see groups of insects scuttling around on your squash plants, they probably are squash bug nymphs.
These feed on the squash plants – leaves and fruits – and they can cause a lot of damage. An even bigger problem is that they can carry a squash disease called Cucurbit Yellow Vine, which can definitely kill your plants.
The adults and nymphs can be removed by knocking them into a tub of soapy water. It is a good idea, though, to check your plants for squash bug eggs.
You can use a piece of clear packing tape or a piece of duct tape to remove the eggs from your plants. Just press the sticky side of the tape to the collection of shiny eggs, remove the tape, fold it over, and smash the eggs inside the tape. Simple!
Removing all the eggs will help keep the population of adults and nymphs to a much lower level, which will limit the amount of damage they can do to your plants and reduce the risk of Cucurbit Yellow Vine.
Summer squash in the Southern garden also is attacked by mildew diseases, both downy mildew and powdery mildew. If your plants die earlier in the summer, then these will not be a problem, because the mildews usually appear after mid-summer.
Downy mildew arrives at a slightly different time each summer in upper parts of the South. It can’t survive our winters, but it comes up from Florida where it survives just fine. If the petioles (leaf stems) are still standing up on your plants, but the leaves look brown and droopy, then downy mildew is a likely cause. There is no effective spray or treatment for downy mildew, but preventive care can help.
Leaf diseases like downy mildew (and powdery mildew) need leaf wetness to infect the leaves and grow. Keeping the leaves dry as much as possible, by careful watering, can delay infection. Increasing air-flow around the leaves, so they dry faster after a rain, also helps. Remove weeds as much as possible, and allow plenty of space between plants.
Also, healthy, well-grown plants get less disease than puny plants. Just like for squash vine borers, consider whether you might need to side-dress your plants with fertilizer or compost to improve their condition.
Powdery mildew becomes a big problem in warm, humid conditions. Since that pretty much describes several months of weather across the entire Southeast, it is a safe bet that powdery mildew will find your plants eventually.
Treating Mildews in Organic Gardens
For both downy and powdery mildews, the bacterial product Serenade, which is organic-approved, can slow down the rate of infection. It should be applied to plants every 7-10 days, before any sign of infection is seen. If you see signs of disease on your plants (mottled or brown spots on leaves, for example), it is too late to get much benefit from using the product.
In a couple of Cobb County community gardens, the use of Serenade has helped extend the “squash season” for local gardeners. If your squash patch has suffered from mildew attack in past years, you might consider trying the spray, but do not wait much longer to start. By July, infection may already have begun.
Another option is to spray with homemade products of either compost tea (one gallon of well-aged compost in a five gallon bucket filled with water, soaked for three days, then strained to use in a spray bottle) or a baking-soda spray, both of which can slow down an infection. Neither of these has been shown to work as well as Serenade (which works less well than chemical fungicides), but some gardeners like to try the DIY route first.
If you are a DIY gardener, this is the recipe for baking-soda spray recipe from one of my Rodale gardening books:
Dissolve 1 teaspoon of baking soda in a quart of warm water, with up to a teaspoon of dish soap or insecticidal soap added. Spray the leaves, including the undersides.
For both compost tea and the baking soda solution, apply to plants much more frequently than the Serenade.
Hoping for Plenty of Summer Squash from the Southern Garden
Summer squashes seem to be an essential vegetable in the South. They are the base of many favorite “church casseroles” – dishes that fill the tables at summertime potluck suppers and appear at your door in hard times. I don’t remember seeing squash-casseroles when I was growing up in Oklahoma, but I certainly have seen (and enjoyed) many since moving to Georgia. In the South, the squash harvest is important.
The garden/farm where Joe and I used to volunteer got around squash-plant losses by planting MANY squash plants over several weeks. Even when some plants died, more remained and produced squash. If the squash harvest didn’t look abundant enough, we just planted more.
In home gardens, this approach is not really feasible. Hence, the long blog post about upcoming problems with summer squash in the Southern garden.
Best wishes for a squash-filled summer!